1. Field of Invention
This invention relates to a tool for servicing a nuclear reactor pressure vessel and specifically a tool for permitting closure of a normally submersed fluid outlet in a reactor pressure vessel. During a refueling and maintenance outage of a nuclear boiling water reactor, there is a need to facilitate isolation and drainage of the recirculation suction piping without draining the reactor vessel. In the past, maintenance and repair activity in the recirculation suction piping has required that the reactor vessel be drained to a level below the elevation of the side mounted recirculation outlet nozzle. Because the outlet nozzle is generally located at an elevation below the radioactive core, the entire core must be off loaded before the cooling fluid can be drained. This procedure is undesirable because it is costly, requires handling and storage of radioactive materials and is time consuming.
2. Description of the Prior Art
In the past, valves in the outlet piping have been provided adjacent the outlet nozzle of the recirculation loop. However, such valves are in need of periodic maintenance which cannot be performed when such a valve is in use. Moreover, such valves have also been found to be subject to fluid leakage if not maintained.
Heretofore, it has not been believed practical to provide means for closing off the submersed inlet to the first valve due to the relatively high pressures, close side wall tolerances of a reactor vessel and irregularities in the nozzle throat thought to prevent secure sealing and blockage.